The present invention relates to an envelope generating apparatus for generating an envelope from an input waveform signal, and to an apparatus for approximating an extracted envelope by a line diagram function or an exponential function.
In electronic musical instruments, a natural musical tone generated by playing the instrument is simulated. The simulation is progressively performed by varying various types of factors or parameters defining the natural musical tone in a try and error manner. In the simulation, an operator once sets, and hears the musical tone formed using the set parameters to check if the sounded musical tone is good. If it is no good, he sets again another modified parameters seeming to be correct. At the present stage of technology in this field, there has not been developed any effective measure to approximating the artificial musical tone generated by the musical instrument to the natural musical tone. This complies with the operator to use the try-and-error process for the musical tone simulation. The restricted parameters used make it difficult to obtain a satisfactory approximation of the artificial musical tone to the natural one.
The same thing is true for generating an envelope as one of factors of the waveform.
In the apparatus to compose a musical tone by multiplying the one wave data at the fundamental frequency of a musical tone by the envelope data, it is impossible to form an envelope whose variation is complicated. Only one freedom allowed in this case is to generate a monotone waveform, e.g., an exponential curve, in a confined period of time or interval, and to change the ends of the interval.
Thus, the present artificial sound composing measure is under limited conditions of hardware and software, and is only the perceptional and try-and-error process under limited conditions and with also limited freedom of design.
Sampling musical instruments have been known. In the instrument, the waveform of a natural musical tone is sampled using the PCM technique. The sampled and stored waveform data are read out in real time for sounding. This instrument can reproduce the sampled sound at high fidelity. The musical tone data of the instrument takes the form of a complete waveform, and is inappropriate for the machine computing processing. For this reason, when using the sampling instrument, it is impossible to reproduce the features of the complicatedly varying musical tone by the natural musical instrument by using the sampled data of one waveform. Thus, it is enough to say that the conventional sound composing system as mentioned above abandons the technical efforts to electronically synthesize sounds from the outset.
For the above background reasons, the present invention has been made on the hypothesis that the following approach would be effective to approximate the articifial musical tone to the natural musical tone: the waveform of a musical tone by the natural musical instrument is analyzed, the features of the waveform are extracted on the basis of the analyzed data, and the extracted feature parameters of the waveform are used for synthesizing or composing an aritificial musical tone well approximating the natural musical tone.